Sensing device for controlling the movement of sheet stock

ABSTRACT

A sensing device including a support, an arm pivotally mounted on the support by a low friction connection, and a switch responsive to the angular position of the arm for controlling stock movement. The switch is of the type which requires no energy to operate it. The low friction connection includes a ball and a cooperating recess along the pivotal axis of the arm. A weight is mounted on the arm so that it can be moved toward and away from the pivotal axis.

nited States Patent [191 111 3,825,204 Vinson July 23, 1974 [54] SENSING DEVICE FOR CONTROLLING 2,115,737 5/1938 Menschner 242/753 X THEMOVEMENT 0 SHEET STOCK 2,737,089 3/1956 Baumgartner 3,225,989 12/1965 Stine 242/753 X [76] Inventor: Paul Vinson, 7821 N. 65th St.,

I Scottsdale 85253 Primary Examiner-John W. l-luckert [22] Filed: Sept. 20, 1972 Assistant Examiner-Milton S. Gerstein 1 pp NO 290 460 Attorney, Agent, or Firm-Smyth, Roston & Pavitt v 57 ABSTRACT [52] US. Cl. 242/753, 242/7542, 242/755, 1

308/1316 10 A sensing device including a support, an arm prvotally [51] Int CL 1365b 25/20 mounted on the support by a low friction connection, [58] Field 75 5 75 42 and a switch responsive to the angular position of the f 42/75 8 5 arm for controlling stock movement. The switch is of the type which requires no energy to operate it. The [56] References Cited low friction connection includes a ball and a cooperating recess along the pivotal axis of the arm. A weight UNITED STATES PATENTS is mounted on the arm so that it can be moved toward Mittinger and away from the pivotal axis 1,868,310 7/1932 Cline 242/7543 2,005,738 6/1935 Foster et al 242/7543 X 18 Claims, 5 Drawing Figures PATENTEBJULZSIQH 3.8125204 sum 20F 2 "H HIIHII. WWI. I] I 1/ w 1 e) I Q a? V V I 17' 7.9 9? 7f 9/ BACKGROUND OF THE INVENTION In the movement of sheet material such as strip stock, it is often necessary to provide a control function which is dependent upon the amount of slack in the stock at a particular location. For example, in feeding strip stock to a press, there should be ample slack in the stock to avoid placing the stock in tension, but insufficient slackto prevent the stock from becoming tangled or creating other problems.

A sensing device responsive to the slack in the stock is used'to control the feeding of the stock to the press. For heavy', stiff materials an insensitive sensing device may be used; however,- for lightweight, flexible stock, the-sensing device must be very sensitive. Heretofore, sensing devices of this kind have not been sufficiently sensitive for use with lightweight, flexible stock.

SUMMARY OF THE INVENTION The present invention provides a sensing device which is very sensitive and can be effectively used with lightweight, flexible stock. In addition, the sensitivity can be adjusted so that the sensing device can accommodate stock of different weights.

Generally the sensing device includes a support,'an arm, means for mounting the arm on the support for pivotal movement about a pivotal axis, and switch means responsive to the angular position of the arm for controlling the feeding of the sheet stock. In use the stock is adapted to move across the arm with some of the stock resting on the arm at a location spaced from the pivotal axis. Any slack in the stock at such location tends to pivot the arm-about the pivotal axis, and accordingly pivotal movement of the arm is dependent upon the slack in the stock.

To make the arm pivot in response to very lightweight stock, the present invention provides for low friction means for mounting-the arm for pivotal move ment. Such low friction means can advantageously include a ball and wall means defining a recess. The ball is at least partially received by the recess and engages the wall means. The ball is attached to either the support or the arm, and the recess is provided on the other of the support and the arm. The resulting line contact between the ball and the wall means of the recess results in a very low friction connection for the arm and the support. This enhances the sensitivity of the sensing device. V

The switch means is actuated by the arm. The present invention further increases sensitivity of the sensing device by employing a switch which requires substantially zero energy to actuate. For example, such a switch mayinclude a photocell and alight or a proximity switch. Switches of this type require substantially no energy for actuation, whereas the usual snap action switch requires a force which the relatively lightweight sheet stock may not be able to generate. Thus, the sheet stock need only generate sufficient force to overcome the very low friction of the arm mounting means.

The present invention provides for varying the sensitivity of the sensing device. This can be accomplished by mounting a weight on the arm for movement toward and away from the pivotal axis of the arm. By appropriately moving the weight, the sensing device can be made less sensitive so that it can accommodate heavier stock. To permit a finer adjustment, two of these weights may be provided on opposite sides of the pivotal axis with one of the weights being heavier than the other. By making the arm less sensitive, the sensing device may provide, for example, a relatively large loop of relatively heavy material.' 7

The switch-means can also be adjusted so that it is actuated at different angular positions of the arm. To this end, the switch means may include a first switch element carried by the arm and second and third switch elements mounted on the support. For example, the

first switch element may be a light, and each of the second and third switch elements may be a photocell. The switch can be opened by bringing the lightnear the first photocell and closed by bringing the light near the second photocell. With the present invention, the two photocells are mounted on the support for movement so that the angular position of the arm at which switch actuationoccurs can be adjusted.

In a preferred construction, the support includes a plate supported in a generally horizontal plane above a supporting surface and having a slot therein. The support includes first and second sections carried by the plate and projecting downwardly from the plate. The arm is mounted on the first and second sections for pivotal movement and projects into registry with the slot.

A stock reel is mounted on the plate and a guide is provided on the plate for guiding the stock across the plate. Y

The inventioncan best be'understood by reference to I the following description taken in connection with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan viewv of a sensing device constructed in accordance with the teachings of this invention. The mounting leg for the reel is shown in section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sensing device ll'constructed in accordance'with the teachings of this invention. The sensing device 11 generally includes a support 13, a reel 15 (FIGS. 2 and 3), a motor 17 for driving the reel, a balanced treadle arm 19 pivotally mounted on the supgenerally along line port, and a control element or switch 21 operable by. thejarm to controlthe motor 17. The support 13 includes a plate 23 and a pair of spaced parallel runners 25 suitably attached to the plate as by screws 27. One end of the plate 23 is formed with a tapered slot 29 which terminates in an end surface 31. The plate 23 is provided with a groove 33 in the upper surface thereof which extends to a location adjacent a pair of guides 35 and which is of progressively decreasing depth as it extends toward the guides. In theembodiment illustrated the guides 35 are in the form of bars which extend in spaced, parallel relationship and which are mounted on the plate 23 in any suitable manner such as by screws The reel is supported above the plate 23 and the slot 29 by a plate-like leg 39. The motor 17 drives the reel 15 through a gear box 41, and the motor and the gear box are also supported by the leg 39. Although the motor 17 could be of various constructions, in the embodiment illustrated, it is a stepping motor.

The reel 15 is mounted on a shaft 42 of the gear box 41. The reel 15 has a hub 43 on which sheet material in th form of strip stock 45 is adapted to be wound. When the strip stock 45 on the reel 15 has been depleted, a knob 46 is unscrewed to permit the entire reel or at least the hub 43 thereof to be removed, and a new reel or hub 43 is mounted on the shaft 42. The strip stock 45 extends from the reel 15 downwardly to the slot 29 and across the support 13 to a utilization apparatus such as press 47 (FIGS. 1 and 2). The slot 29, the groove 33, and the guide 35 guide the strip stock 45 across the support 13.

FIGS. 2 and 4 show a preferred form of low friction pivotal mount for the arm 19. The support 13 includes a pair of spaced parallel sections or flanges 49 and 51 which are suitably attached to a web 53. The web 53 is attached to the underside of the plate 23 by screws 55.

The arm 19 includes an elongated plate 57 and a block 59 suitably rigidly attached to the underside of the tongue. The block 59 has a cylindrical bore 61 extending therethrough. Bushings 63 of a hard material such as carbide are mounted in the opposite ends of the bore 61. Each of the bushings has a conical seat 65 at the outer end thereof with the conical seat being flared radially outwardly as it extends axially downwardly.

Each of the flanges 49 and 51 has a threaded stud 67 therein with a ball 69 of hard material such as carbide brazed or otherwise affixed to the inner end thereof. Each of the balls 69 engages the associated seat 65 and is partially received in the recess formed by the seat. The surfaces of the balls 69 and the seat 65 are preferably smooth and hard. The balls 69 and the seats 65 define a pivotal axis for the arm 19. The axial load which the balls 69 apply to the bushings 63 can be adjusted by turning of the threaded studs 67. When the studs 67 have been appropriately axially positioned, lock nuts 71 are tightened on the studs 67 to securely lock the studs in position.

The seats 65 should be defined by a hard surface to minimize wear and to maintain friction at a minimum. The seat 65 could be provided in the stud 67. However, in this event, the stud 67 would have to be constructed of a hard material such as carbide, and it is difficult to thread carbide. For this reason, it is preferred to have the seat 65 in the bushing 63 and to mount the ball 69 on the stud 67.

With the arm 19 mounted in this fashion, a portion 73 of the arm 19 projects into registry with the slot 29. Another portion of the arm 19 extends in the opposite direction from the pivotal axis of the arm. The force required on the portion 73 to pivot the arm 19 can be adjusted by a pair of weights 75 and 77 which are mounted on a threaded stud 79 received in the block 59. Each of the weights 75 and 77 forms a nut so that the distance between such weight and the pivotal axis of the arm 19 can be adjusted by turning of the weight. The stud 79 is held against rotation relative to the block 59. The weights 75 and 77 preferably form an interference fit with the stud 79 so that inadvertent rotation of the weights will not occur. One of the weights and 77 weighs more than the other to permit finer adjustment of the force necessary to pivot the arm. These weights 75 and 77 can be changed from side to side or placed on the same side of the pivot axis if desirable to balance different material weights.

To increase sensitivity of the arm 19, no energy is required to actuate the switch 21. Although the switch 21 could take different forms, in the embodiment illustrated, it includes a switch element or light 81 (FIG. 2) mounted on a bracket 83 carried by the arm 19 and a pair of switch elements or photocells 85 and 87 (FIGS. 2 and 5). An arcuate slot 89 in the flange 51 allows the light 81, when properly positioned, to actuate either of the photocells 85 and 87. The photocells 85 and 87 are mounted on pivotal links 91, respectively, which are pivotally mounted on an extension 93 of the stud 67 (FIGS. 4 and 5) and retained thereon by a nut 95. The photocells 85 and 87 may project into the slot 89 so that when the light 81 is brought adjacent one of the photocells, there is only a very slight clearance space between the light and the photocell.

When the arm 19 is pivoted to bring the light 81 in line with the photocell 85, appropriate conventional circuitry deenergizes the motor 17, and when the light 81 is brought into alignment with the photocell 87, the motor is energized. The angular orientation of the arm 19 at which either of these motor control functions occurs, can be adjusted by loosening the nut 95 and pivoting one or both of the arms 91 to a new position.

The press 47 includes its own feed mechanism (not shown) which controls the rate of utilization of the strip stock by the press. It is important that the sensing device 11 provide ample slack in the strip stock 45 so that the demands of the press for stock can be fully met. On the other hand, it is important that this slack not be too great. In the embodiment illustrated, the sensing device 11 is mounted on the press 47 by screws 96 (only one being shown in FIG. 2).

The motor 17 drives the reel 15 to unwind the strip stock 45. To the extent that the unwound strip stock 45 is not used by the press 47, it forms slack in the form of aloop 97. The weight of the loop 97 bears against the portion 73 of the arm 19 and tends to pivot the arm clockwise as viewed in FIG. 2. Thus, the weight or clockwise torque applied to the arm 19 is a function of the slack in the strip stock or the size of the loop 97. The arm 19 is weighted so as to tend to pivot counterclockwise as viewed in FIG. 2, and this counterclockwise torque resists the clockwise torque caused by the loop 97 to allow enlargement of the loop.

Eventually the weight of the loop 97 will be sufficient to pivot the arm 19 clockwise as viewed in FIG. 2 to bring the light 81 into alignment with the photocell 85. This actuates the zero energy switch 21 to deenergize the motor 17,-whereupon the motor 17 and the reel 15 stop immediately. As the press 47 continues to use sheet stock 45 the loop 97 of sheet material is progressively used up and the arm 19 ultimately pivots counterclockwise under the influence of its own weight and the weights 75 and 77 to bring the light 81 into registry with the photocell 87 to start the motor 17. Appropriate stops (not shown) may be provided to limit the pivotal movement of the arm 19.

The stiffness of the strip 45 may also affect the size of the loop 97 which actuates the switch 21. However,

the weights 75 and 77 may be adjusted to compensate for stiffness of the strip stock 45. The sensing device 11 is adapted for use with strip stock which is very flexible and which has virtually no stiffness.

The mounting meansfor the arm 19 shown in FIG. 4 provides for low friction pivotal movement of the arm 19, and the switch 21 can be actuated without extracting any energy from the arm 19. The sensitivity of the device 11 can be adjusted by turning the weights 75 and 77 to thereby adjust the counterclockwise torque on the arm 19. The angular position of the arm 19 at which the motor is energized or deenergized can be simply adjusted by moving of the links 91.

Although the switch 21 in the embodiment shown in FIGS. 15 includes the light 81 and the photocells 85 and 87, obviously other zero energy switches can be employed. For example, the light and photocell may be arranged in other ways and a masking device may be employed if desired as one of the switch elements to cause activation and deactivation'of the photocells. Alternatively, each of the photocells 85 and 87 may be replaced with a proximity switch and the arm 19 may be constructed of a material, or'carry an element, for actuating the proximity switch.

The switch 21 can be used for control elements other than the motor 17. For example, the switch 21 could be used to control the operation of straightening rolls which in turn would control the size of the loop 97.

Although an exemplary embodiment of the invention has been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

1 claim: 1. A sensing device for controlling stock movement comprising: i

a support;

an arm; means for mounting the arm on the support for pivotal movement about a pivotal axis, the stock being adapted to move across the arm with at least some of the stock resting on the arm at a location spaced from the pivotal axis so that the stock tends to pivot the arm about said pivotal axis whereby pivotable movement of the arm about said pivotable axis is stock dependent; a zero energy switch including a first switch element mounted on the support and a second switch element drivable by the arm and pivotable therewith about the pivotal axis; and said switch including means responsive to said second switch element being in a first predetermined position about said pivotal axis relative to said first switchelement' for actuating said switch without absorbing energy from said arm, said switch being useable to control the stock movement across said arm.

2. A sensing element as defined in claim 1 wherein at least one of said switch elements includes a photo sensitive unit. l

3. A sensing device as defined in claim 1 wherein at least one of said switch elements includes a proximity switch. Y

4. A sensing device defined in claim 1 including stock drive means for moving the stock across said arm, said switch controlling said stock drive means.

5. A sensing device as defined in claim 1 wherein said first switch element is mounted for movement on said support whereby the location of said first predetermined position can be adjusted.

6. A sensing device as defined in claim 1 wherein said switch includes a third switch element mounted on said support and spaced from said first switch element, said switch being opened and closed, respectively, when the second switch element reaches said first predetermined position and a second predetermined position about said pivotal axis relative to said third switch element.

7. A sensing device as defined in claim 1 wherein said pivotal axis has a horizontal component, said sensing device includes a weight and means for mounting said weight on said am for movement toward and away from said pivotal axis whereby the force required to pivot said arm about said pivotal axis can be adjusted.

8. A sensing device as defined in claim 1 wherein said means for pivotally mounting includes a ball carried by one of the arm and the support and a recess for at least partially receiving the ball provided on the other of the arm and the support, said ball and said recess being located along said pivotal axis.

9. A sensing device as claimed in claim 8 wherein said pivotal axis has a horizontal component, said sensing device includes a weight and means for mounting said weight on said arm for movement towardand away from said pivotal axis whereby the force required to pivot said arm aboutsaid pivotal axis can be adjusted.

10. A sensing device for controlling stock movement comprising:

a support;

an arm;

means for mounting the arm on the support for pivotal movement about a pivotal axis, the stock being adapted to move across the arm with at least some of the stock resting on the'arm at a location spaced from the pivotal axis so that the stock can pivot the arm about said pivotal axis whereby pivotal movement of the arm about said pivotal axis is stock dependent;

said pivotal axis having a horizontal component;

a weight;

means for mounting the weight on said armfor movement toward and away from the pivotal axis whereby the resistance of the arm to being pivoted by the stock can be adjusted;

a control element operable by the arm, said control element being useable to control the movement of the stock across the arm; and

said means for pivotally mounting includes a ball carried by one of the arm and the support and a recess for at least partially receiving the ball provided on the other of the arm and the support, said ball and said recess being located along said pivotal axis.

11. A sensing device as defined in claim l0'including a bushing carried by said arm and defining said recess, said ball being carried by said recess, said sensing device including a threaded member carried by said support for loading the ball against said bushing in a direction axially of the pivotal axis.

12. A sensing device as defined in claim 10 including a second weight and means for mounting said second weight on the arm for movement toward and away from the pivotal axis on the side thereof generally opposite to the first mentioned weight, said first mentioned weight weighing more than said second weight.

13. A sensing device as defined in claim 10 including drive means for moving the stock across the arm, said control element controlling the stock drive means.

14. A stock reel comprising:

a support including a plate and means for mounting said plate in a generally horizontal position above a supporting surface, said plate having a slot therein;

said support including first and second sections carried by said plate and projecting downwardly therefrom;

an arm;

means for mounting said arm on said sections for pivotal movement relative thereto about a pivotal axis, at least a portion of said arm lying between said sections, said arm extending into registry with said slot;

a reel on which the stock is adapted to be wound;

means for mounting the reel on the support for rotation relative thereto;

a motor for driving the reel;

the stock being adapted to extend between the reel and the arm, the stock being adapted to move across the arm with at least some of the stock resting on the arm at a location spaced from the pivotal axis so that the stock tends to pivot the arm about the pivotal axis whereby pivotal movement of the arm about said pivotal axis is stock dependent; switch means responsive to the arm being in a first position about said pivotal axis for turning the motor on and responsive to the arm being in a sec- 8 ond position about said pivotal axis for turning the motor off; and

guide means on the plate for guiding the stock across the plate.

15'. A stock reel as defined in claim 14 wherein said switch means is a zero energy switch means and said arm mounting means is of the low friction type and includes at least one ball.

16. A device for controlling the movement of stock to a utilization apparatus comprising:

a support;

means on said support for rotatably mounting a reel adapted to have the stock wound thereon;

motor means for driving the reel;

the stock being adapted to extend downwardly from the reel to form a loop and then to the utilization apparatus with the size and weight of said loop varying with the rate of supply of the stock from said reel and the rate of utilization of the stock by said utilization apparatus;

control means for controlling said motor means as a function of the size of said loop whereby the control of the feeding of the stock to the utilization apparatus is controlled; and

said control means including switch means responsive to said loop for controlling said motor means, said switch means being free of a driving relationship with said loop.

17. A device as defined in claim 16 wherein said switch means includes a proximity switch.

18. A device as defined in claim 16 wherein said switch means includes a photo sensitive unit. 

1. A sensing device for controlling stock movement comprising: a support; an arm; means for mounting the arm on the support for pivotal movement about a pivotal axis, the stock being adapted to move across the arm with at least some of the stock resting on the arm at a location spaced from the pivotal axis so that the stock tends to pivot the arm about said pivotal axis whereby pivotable movement of the arm about said pivotable axis is stock dependent; a zero energy switch including a first switch element mounted on the support and a second switch element drivable by the arm and pivotable therewith about the pivotal axis; and said switch including means responsive to said second switch element being in a first predetermined position about said pivotal axis relative to said first switch element for actuating said switch without absorbing energy from said arm, said switch being useable to control the stock movement across said arm.
 2. A sensing element as defined in claim 1 wherein at least one of said switch elements includes a photo sensitive unit.
 3. A sensing device as defined in claim 1 wherein at least one of said switch elements includes a proximity switch.
 4. A sensing device defined in claim 1 including stock drive means for moving the stock across said arm, said switch controlling said stock drive means.
 5. A sensing device as defined in claim 1 wherein said first switch element is mounted for movement on said support whereby the location of said first predetermined position can be adjusted.
 6. A sensing device as defined in claim 1 wherein said switch includes a third switch element mounted on said support and spaced from said first switch element, said switch being opened and closed, respectively, when the second switch element reaches said first predetermined position and a second predetermined position about said pivotal axis relative to said third switch element.
 7. A sensing device as defined in claim 1 wherein said pivotal axis has a horizontal component, said sensing device includes a weight and means for mounting said weight on said arm for movement toward and away from said pivotal axis whereby the force required to pivot said arm about said pivotal axis can be adjusted.
 8. A sensing device as defined in claim 1 wherein said means for pivotally mounting includes a ball carried by one of the arm and the support and a recess for at least partially receiving the ball provided on the other of the arm and the support, said ball and said recess being located along said pivotal axis.
 9. A sensing device as claimed in claim 8 wherein said pivotal axis has a horizontal component, said sensing device includes a weight and means for mounting said weight on said arm for movement toward and away from said pivotal axis whereby the force required to pivot said arm about said pivotal axis can be adjusted.
 10. A sensing device for controlling stock movement comprising: a support; an arm; means for mounting the arm on the support for pivotal movement about a pivotal axis, the stock being adapted to move across the arm with at least some of the stock resting on the arm at a location spaced from the pivotal axis so that the stock can pivot the arm about said pivotal axis whereby pivotal movement of the arm about said pivotal axis is stock dependent; said pivotal axis having a horizontal component; a weight; means for mounting the weight on said arm for movement toward and away from the pivotal axis whereby the resistance of the arm to being pivoted by the stock can be adjusted; a control element operable by the arm, said control element being useable to control the movement of the stock acRoss the arm; and said means for pivotally mounting includes a ball carried by one of the arm and the support and a recess for at least partially receiving the ball provided on the other of the arm and the support, said ball and said recess being located along said pivotal axis.
 11. A sensing device as defined in claim 10 including a bushing carried by said arm and defining said recess, said ball being carried by said recess, said sensing device including a threaded member carried by said support for loading the ball against said bushing in a direction axially of the pivotal axis.
 12. A sensing device as defined in claim 10 including a second weight and means for mounting said second weight on the arm for movement toward and away from the pivotal axis on the side thereof generally opposite to the first mentioned weight, said first mentioned weight weighing more than said second weight.
 13. A sensing device as defined in claim 10 including drive means for moving the stock across the arm, said control element controlling the stock drive means.
 14. A stock reel comprising: a support including a plate and means for mounting said plate in a generally horizontal position above a supporting surface, said plate having a slot therein; said support including first and second sections carried by said plate and projecting downwardly therefrom; an arm; means for mounting said arm on said sections for pivotal movement relative thereto about a pivotal axis, at least a portion of said arm lying between said sections, said arm extending into registry with said slot; a reel on which the stock is adapted to be wound; means for mounting the reel on the support for rotation relative thereto; a motor for driving the reel; the stock being adapted to extend between the reel and the arm, the stock being adapted to move across the arm with at least some of the stock resting on the arm at a location spaced from the pivotal axis so that the stock tends to pivot the arm about the pivotal axis whereby pivotal movement of the arm about said pivotal axis is stock dependent; switch means responsive to the arm being in a first position about said pivotal axis for turning the motor on and responsive to the arm being in a second position about said pivotal axis for turning the motor off; and guide means on the plate for guiding the stock across the plate.
 15. A stock reel as defined in claim 14 wherein said switch means is a zero energy switch means and said arm mounting means is of the low friction type and includes at least one ball.
 16. A device for controlling the movement of stock to a utilization apparatus comprising: a support; means on said support for rotatably mounting a reel adapted to have the stock wound thereon; motor means for driving the reel; the stock being adapted to extend downwardly from the reel to form a loop and then to the utilization apparatus with the size and weight of said loop varying with the rate of supply of the stock from said reel and the rate of utilization of the stock by said utilization apparatus; control means for controlling said motor means as a function of the size of said loop whereby the control of the feeding of the stock to the utilization apparatus is controlled; and said control means including switch means responsive to said loop for controlling said motor means, said switch means being free of a driving relationship with said loop.
 17. A device as defined in claim 16 wherein said switch means includes a proximity switch.
 18. A device as defined in claim 16 wherein said switch means includes a photo sensitive unit. 